In a recent study of 86 working adults, the mean number of hours per week spent talking on the phone was 21.6. The sd= 5.7 hours. Calculate the 90% confidence level for the mean.
The format for writing a confidence interval is (xx.x, xx.x)
Please see the attachments.
Since the sample is fairly large, we can use the normal distribution for the construction of CI.
The confidence interval is given by , where = 21.6, σ = 5.7, n = ...
The expert determines the confidence intervals for a study of working adults.